The LTE (Long Term Evolution) system defined by 3GPP (3rd Generation Partnership Project) employs MIMO (Multiple Input Multiple Output) transmission, which uses a plurality of transmission/reception antennas in a radio base station apparatus, to realize higher speed transmissions. Using this MIMO transmission, it is possible to perform scheduling in the space domain, in addition to scheduling in the time domain•frequency domain. MIMO transmission includes single-user MIMO (SU-MIMO) which transmits a plurality of signals from a radio base station apparatus having a plurality of antennas, to a single user (mobile terminal apparatus), in a parallel fashion, and multi-user MIMO (MU-MIMO) which performs transmission by applying space multiplexing to a plurality of users (mobile terminal apparatuses), from a radio base station apparatus having a plurality of antennas (SDMA: Space Division Multiple Access).
SU-MIMO is a method of transmitting different data from a plurality of transmission antennas of a transmitter, separating the data in a receiver into signals from the respective transmission antennas, and demodulating these signals. That is to say, as illustrated in FIG. 1, in the transmitter, different data having been processed in separate transmission circuits 1 to NTX is transmitted as transmission signals from separate antennas 1 to NTX. The signals having past the propagation path are received by separate antennas 1 to NRX. At this time, different data is in a state of being mixed up. At the receiver, the data is received by separate antennas, and the data processed in reception circuits 1 to NRX is subjected to signal separation in a signal separation section, and different data is demodulated (non-patent literature 1).
As for the method of separating signals in the receiver, there are a signal separation method (MMSE method) by the MMSE (Minimum Mean Square Error) algorithm which minimizes interference and noise power, a method of separating signals by repeating removing replicas of the stream of the best quality in a cascade fashion from a received signal by space filtering (SIC (Successive Interference Canceller) method), and a method of calculating replicas of received signal points, using channel information, with respect to all possible combinations of transmission signals, and finding the closest point among them (MLD (Maximum Likelihood Detection) method).